package com.base.util;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;


/**
 *
 * 类名称：	RSAUtils
 * 类描述：	RSA公钥/私钥/签名工具包
 * 字符串格式的密钥在未在特殊说明情况下都为BASE64编码格式<br/>
 * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/>
 * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
 * 创建人：  张本学
 * 创建时间：2017年7月17日 下午1:18:19
 * 修改人：
 * 修改时间：
 * @version 1.0.0
 */
@SuppressWarnings("all")
public class RSAUtils {

    /** 
     * 加密算法RSA
     */
    public static final String KEY_ALGORITHM = "RSA";
    
    /** 
     * 签名算法
     */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    /** 
     * 获取公钥的key
     */
    private static final String PUBLIC_KEY = "RSAPublicKey";
    
    /** 
     * 获取私钥的key
     */
    private static final String PRIVATE_KEY = "RSAPrivateKey";
    
    /** 
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 117;
    
    /** 
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 128;

    /**
     * RSA密钥长度 默认1024位， 密钥长度必须是64的倍数， 范围在512至65536位之间。
     */
    private static final int KEY_SIZE = 1024;

    /** 
     * <p>
     * 生成密钥对(公钥和私钥)
     * </p>
     * @return  生成密钥对(公钥和私钥)
     * @throws Exception
     */
    public static Map<String, Object> genKeyPair() throws Exception {
        // 实例化密钥对儿生成器
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        // 初始化密钥对儿生成器
        keyPairGen.initialize(KEY_SIZE);
        // 生成密钥对儿
        KeyPair keyPair = keyPairGen.generateKeyPair();
        // 公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        // 私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        // 封装密钥
        Map<String, Object> keyMap = new HashMap<String, Object>(2);
        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }
    
    /** 
     * <p>
     * 用私钥对信息生成数字签名
     * </p>
     * @param       data        已加密数据
     * @param       privateKey 私钥(BASE64编码)
     * @return  用私钥对信息生成数字签名
     * @throws  Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        // 转换私钥材料
        byte[] keyBytes = Base64.getDecoder().decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        // 实例化密钥工厂
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 取私钥匙对象
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        // 实例化Signature
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        // 初始化Signature
        signature.initSign(privateK);
        // 更新
        signature.update(data);
        // 签名
        return Base64.getEncoder().encodeToString(signature.sign());
    }

    /** 
     * <p>
     * 校验数字签名
     * </p>
     * @param       data        已加密数据
     * @param       publicKey   公钥(BASE64编码)
     * @param       sign        数字签名
     * @return  boolean 校验成功返回true 失败返回false
     * @throws Exception
     */
    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {
        // 转换公钥材料
        byte[] keyBytes = Base64.getDecoder().decode(publicKey);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        // 实例化密钥工厂
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 生成公钥
        PublicKey publicK = keyFactory.generatePublic(keySpec);
        // 实例化Signature
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        // 初始化Signature
        signature.initVerify(publicK);
        // 更新
        signature.update(data);
        // 验证
        return signature.verify(Base64.getDecoder().decode(sign));
    }

    /** 
     * <P>
     * 私钥解密
     * </p>
     * @param       encryptedData   已加密数据
     * @param       privateKey      私钥(BASE64编码)
     * @return  解密数据
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey) throws Exception {
        // 取得私钥
        byte[] keyBytes = Base64.getDecoder().decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 生成私钥
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /** 
     * <p>
     * 公钥解密
     * </p>
     * @param       encryptedData   已加密数据
     * @param       publicKey       公钥(BASE64编码)
     * @return 解密数据
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {
        // 取得公钥
        byte[] keyBytes = Base64.getDecoder().decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 生成公钥
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /** 
     * <p>
     * 公钥加密
     * </p>
     * @param       data        源数据
     * @param       publicKey   公钥(BASE64编码)
     * @return 加密数据
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
        // 取得公钥
        byte[] keyBytes = Base64.getDecoder().decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /** 
     * <p>
     * 私钥加密
     * </p>
     * @param       data         源数据
     * @param       privateKey  私钥(BASE64编码)
     * @return 加密数据
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {
        // 取得私钥
        byte[] keyBytes = Base64.getDecoder().decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 生成私钥
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /** 
     * <p>
     * 获取私钥
     * </p>
     * @param       keyMap      密钥对
     * @return 私钥
     * @throws Exception
     */
    public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return Base64.getEncoder().encodeToString(key.getEncoded());
    }

    /** 
     * <p>
     * 获取公钥
     * </p>
     * @param       keyMap      密钥对
     * @return 公钥
     * @throws Exception
     */
    public static String getPublicKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return Base64.getEncoder().encodeToString(key.getEncoded());
    }
}
